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Open AcceResearchCrop and non-crop productivity in a traditional maize agroecosystem of the highland of MexicoRosa M González-Amaro1, Angélica Martínez-Bernal2, Francisco Basurto-Peña3 and Heike Vibrans*1
Address: 1Postgrado en Botánica, Colegio de Postgraduados en Ciencias Agrícolas, 56230 Montecillo, Estado de México, México, 2Departamento de Biología, División de Ciencias Biológicas y de la Salud, Universidad Autónoma Metropolitana-Iztapalapa, Apartado Postal 55-535, 09340, DF, México and 3Jardín Botánico, Instituto de Biología, Universidad Nacional Autónoma de México, Apartado Postal 70-614, DF, México

Email: Rosa M González-Amaro - [email protected]; Angélica Martínez-Bernal - [email protected]; Francisco Basurto-Peña - [email protected]; Heike Vibrans* - [email protected]

* Corresponding author

AbstractBackground: In Mexico, the traditional maize cultivation system has resisted intensificationattempts for many decades in some areas, even in some well-connected regions of the temperatehighlands. We suggest that this is due to economics.

Methods: The total useful biomass of several fields in Nanacamilpa, Tlaxcala, are evaluated forproductivity and costs.

Results: Maize grain production is low (1.5 t ha-1) and does not cover costs. However, maizestover demands a relatively high price. If it included, a profit is possible (about 110 US $ ha-1). Weshow that non-crop production (weeds for food and forage) potentially has a higher value than thecrop. It is only partially used, as there are constraints on animal husbandry, but it diversifiesproduction and plays a role as a back-up system in case of crop failure.

Conclusion: The diversified system described is economically rational under current conditionsand labor costs. It is also stable, low-input and ecologically benign, and should be recognized as animportant example of integrated agriculture, though some improvements could be investigated.

BackgroundAgricultural productivity is defined as the yield of usefulproduct per unit land area [1]. The useful product mayhave various dimensions, such as biomass, food value,monetary value, energy content, CO2 fixation, and others[2].

Traditional, small-scale, low-input agriculture is generallyconsidered to have low productivity - both in useful bio-

mass and in monetary value as well as net returns. How-ever, some of the highest-yielding agroecosystems havetraditional characteristics (mixed cropping, labor-inten-sive and input-extensive), particularly home gardens [3].

Traditional practices are sometimes prevalent even inregions with good communications and literate farmerswith access to information, capital or credit, and externalinputs. This is often explained by the conservatism of tra-

Published: 27 November 2009

Journal of Ethnobiology and Ethnomedicine 2009, 5:38 doi:10.1186/1746-4269-5-38

Received: 23 September 2009Accepted: 27 November 2009

This article is available from: http://www.ethnobiomed.com/content/5/1/38

© 2009 González-Amaro et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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ditional farmers [4]. But, alternatively, it could suggestthat some of these systems may have economic advan-tages over more high-input forms of crop production.

One such system exists in the maize-growing region of thehigh valleys and mountains of the center and south ofMexico, with its large urban areas, good communications,relatively good soils and regular rainfall. Modern hybridvarieties and intensive cropping practices have had littlesuccess in this area, though they do exist occasionally. Theuse of chemical fertilizer is common, of herbicides fre-quent, and of some machinery ubiquitous. However,mixed cropping and a relaxed attitude [5] towards weedsare widespread, as is the use of landrace seed and produc-tion mainly for self-consumption. Maize cultivation isoften considered to provide a secure basis from whichother money-earning activities can be pursued. Since theintroduction of large domestic animals by the Spaniards,small-scale farms in the highlands have integrated animalhusbandry and cropping, much more than in the moretropical areas of Mexico.

It is well-known that the traditional Mesoamerican maizecropping system is mixed. Maize, beans and squash arethe most common combination. However, the trend istoward monoculture, even in relatively traditional sys-tems, often because of government incentives.

One important component of productivity in many tradi-tional [6-12] and not-so-traditional agroecosystems [13]is routinely overlooked in economic analysis: the contri-bution of wild-growing plants, or non-crop resources[14]. A decade ago, the Hidden Harvest initiative high-lighted this omission [15]; however, edible and otherwiseuseful "weeds" are still not routinely integrated into pro-ductivity and value analyses. One reason could be thatthey are somewhat difficult to quantify, even by farmersthemselves. They are certainly not part of the data col-lected for official statistics, on which most analyses arebased.

"Wild" in this context is used in the sense of spontaneousor non-cultivated. It does not mean that humans have hadno influence. Many agrestal weeds are highly adapted totheir environment. Several examples from Mexico haveshown that heavily collected weed populations have ahigher allocation to the useful parts, due to selection andpromotion in situ [12,16-18].

Various studies have emphasized the importance of edibleweeds for nutrition, especially of Vitamin A [19-21]. Oth-ers have studied quantities consumed by an average ruralfamily, which is usually about 1 - 15 kg fresh mass/week/family during the appropriate season [10,19,22].

The use of weeds for forage in Mexico has drawn someattention [23-25]. Several studies have focused on thequantities of weeds produced [26,27], or on their compo-sition [26,28]. A study in the Valley of Toluca, CentralMexico [22], has shown that the harvesting of the weedvegetation for fodder elevates the economic return of afield by an average of 50% (in some cases much more).These data were based on a quantification of the actualuse of these plants. This study was conducted in an areawith early-season irrigation and relatively high yields ofmaize grain.

The next step in this line of inquiry is to document thepotential amount and net economic value of the com-bined useful biomass - cultivated and wild - produced bythese semi-traditional maize fields, and in an areadependent on precipitation only. This is the aim of thisstudy.

The study areaNanacamilpa de Mariano Arista is situated in the north-west of the small state of Tlaxcala (Fig. 1) at 2,734 m and19° 27' N, 98° 27 W. The climate is typical of the high-land, marginal tropics with a rainy season in summer, adry season with frosts in winter, and an average annualprecipitation of 700 - 1000 mm. The natural vegetation isa pine-oak forest. The main crops of the area are maize,wheat, beans and barley; there are also some Agave plan-tations for the fermented beverage pulque. Temperatefruit trees such as apples, pears, plums, peaches, and thenative tejocote (Crataegus pubescens (C. Presl) C. Presl)and nopal (Opuntia ficus-indica (L.) Mill.) are grown ingardens and along field margins.

Nanacamilpa is a small town of about 15,000 inhabitants,well-linked on a major highway from Mexico City to Tlax-cala and Veracruz. There are schools, some factories, andmuch commerce, television, telephone and internetaccess. The surrounding villages have paved roads,schools, public transport and other services. The popula-tion is mainly mestizo and Spanish-speaking.

The cropping systemThe main crop, maize, is cultivated in a terraced landscape(Fig. 2). The soil is plowed between November and Febru-ary. Shortly before sowing, the field is harrowed and fur-rows are drawn with a plow, leaving rows 80 cm wide.Traction is either mechanized, by oxen or mules. In Marchseveral seeds are hand-sown 25-40 cm apart in the furrows(listering). The germinated seedlings are fertilized amonth later with urea or manure. Shortly afterwards, thefield is cultivated, to hill the maize and to reduce weedpopulations. This first cohort of weeds is often cut to beused for food and forage. The field is usually hand-weeded



again in the beginning of July; a second fertilization takesplace soon afterwards, when the maize starts to forminflorescences. While the maize is kept mostly weed-freeduring its critical period, from this time on (July), weedsare allowed to develop freely (Fig. 3), and are used mainlyas forage. Though some farmers of the region use herbi-cides, none were used on our study sites. The grain harvestis from November to December. Maize stover is some-times packed mechanically. No pesticides were used in2006, though they are known, available and used if thereis a larger pest problem. The main risks to agriculture are

meteorological - late or early frosts, irregular distributionof rainfall during the rainy season, and hail.

Only one of the surveyed farmers (and none of the studyplot owners) used commercial hybrid seeds in zero-culti-vation, mainly because of its lower labor requirements(others have tried this system, but were not satisfied). Therest used various landrace seeds. The most common vari-eties were called criollo (a cream-colored dent) and azul(a blue-black dent); other reported varieties were gavilán(a cream-colored dent with a longer cob) and chalqueño,a cultivar with larger, wider seeds.

Location of the study area in MexicoFigure 1Location of the study area in Mexico.



Weeds are harvested in April (mainly for food, Fig. 4, 5)and from July to November (mainly for fodder, Fig. 6).

The study year (2006) was considered a relatively goodyear for agriculture in the region, with a rainy season thatstarted early, brought sufficient precipitation, and withouthigh winds, late frosts or hail.

MethodsWritten permission was obtained from the local authori-ties for the field work, and the study protocol wasapproved by the academic institution. The study was car-ried out in two parts. First, a systematic botanical collec-tion of maize field weeds and the plants growing on thefield margins yielded a species list. The vouchers weredeposited at CHAPA and MEXU. Information on plant

uses was obtained through interviews of 56 persons ineach of three communities (a total of 168) of three agegroups and both genders. A field herbarium was used tofacilitate the interviews. The 16 adult informants con-sisted of the owners (man and wife) of four study plots ineach of three communities (see below) and four compara-ble, but non-farming families, selected by a lottery fromcommunity archives. Additionally, a group of 20 children(6-13 yr) and 20 teenagers (14-22 yr; 10 boys and 10 girlseach) from each of these communities were selected fromprimary, secondary and high schools of the study area bylottery, and interviewed.

A typical landscape with terraced maize fields in the study area of Nanacamilpa, Tlaxcala, Mexico, with the Iztaccíhuatl volcano in the backgroundFigure 2A typical landscape with terraced maize fields in the study area of Nanacamilpa, Tlaxcala, Mexico, with the Iztaccíhuatl volcano in the background.

A maize field in August with weeds allowed to grow between the maize plantsFigure 3A maize field in August with weeds allowed to grow between the maize plants.

Harvest of edible wild greens in Nanacamilpa, TlaxcalaFigure 4Harvest of edible wild greens in Nanacamilpa, Tlax-cala.

Sale of edible, wild greens in the Nanacamilpa weekly market (Portulaca oleracea, verdolaga, and Amaranthus hybridus, quin-tonil)Figure 5Sale of edible, wild greens in the Nanacamilpa weekly market (Portulaca oleracea, verdolaga, and Amaran-thus hybridus, quintonil).



Vendors of quelites (wild potherbs) were interviewed atthe weekly market and the permanent market hall toestablish commercial species and prices. In each venuethree vendors were interviewed twice during the year (Fig.5). Prices for maize grain and maize stover tended to bestandard in the region and were elicited during the inter-views and by asking buyers. Prices for non-traded itemssuch as weed forage were established by comparison withfarmgate prices of alfalfa and green maize for forage, com-bined with direct questions on willingness to pay.

The cost of cultivation was considered to be that of con-tracting out operations (plowing, sowing, cultivation, andso on). Labor input in other activities (for example forageharvest) was established by interviews and by participantobservation. The cost of labor was considered to be theregional daily pay for a hired farm hand ("jornal"), whichwas a relatively high 100 pesos (about 9 US dollars) perday. All costs and prices are in Mexican pesos for 2006; theconversion rate to American dollars (US$) varied between10.50 and 11 pesos/dollar in that year.

In a second part, production of useful biomass was stud-ied in fields. The study plots were selected from threecommunities: Nanacamilpa itself, and the villages MiguelLira y Ortega and San Felipe Hidalgo, located about 2 kmof the municipal seat. In each community, 4 fields wereselected for geographical dispersal and the willingness ofthe owners to participate, for a total of 12 study sites. Theowners were interviewed on management practices, costof cultivation, and useful plants.

To measure productivity, we marked rectangles of 7.5 × 7m in a corner of the maize field. Six 1 m2 quadrants weredistributed systematically and marked within the rectan-

gle (Fig. 7). Four of these 1 m2 quadrants were considered"edge" and two were considered "interior". We differenti-ated these because sometimes the vegetation in field bor-ders changes due to better light conditions; also peoplelike to collect wild plants from the margins because theyare more accessible. Most fields were not much wider than15-20 m, so the sampling should be representative.

The biomass of these 6 m2 was harvested twice, in accord-ance with local custom - in April, before the first cultiva-tion, and in July, when forage harvest commences. Thespecies were registered and separated, the individualscounted and the fresh, above-ground biomass measured.Production of maize grain and stover where determinedbased on data from four fields.

ResultsKinds of useful plantsOf the 109 species encountered in the study plots, almosthalf (43) were used for forage. Another 39 species hadmedicinal uses, 18 were considered edible and 10 specieshad other uses (ornamentals, material for handicrafts,construction material, broom-making and fuel). Only 19species were not found to have any known use; 33 specieshad various uses, with the most common combinationsbeing forage-medicinal and forage-food; 4 species hadthree uses (Opuntia spp., Malva parviflora L. and Rumexcrispus L. were used as forage, food and medicinal, andMuhlenbergia macroura (Kunth) Hitchc. served as forage,ornamental and construction (roofing) material).

Commerce with wild plantsThe interviews with the market vendors resulted in a list oftraded species and their prices (Table 1). The list includesfoods, medicinals and condiments. Prices usually rise inthe dry season (October to March or April). The quelites(pot herbs) in this list were the most abundant species in

Harvested weeds mixed with alfalfa for fodderFigure 6Harvested weeds mixed with alfalfa for fodder.

The position of the sampling plots in the maize fieldFigure 7The position of the sampling plots in the maize field.



the study area, but the vendors usually bought their prod-ucts at the wholesale market in Puebla.

During the rainy season, vendors had to compete withhouse-to-house sales of quelites by the farmers; consum-ers preferred this local produce "because it is sure not tocome from irrigated fields" (the products from irrigatedfields have a bad reputation because irrigation water isoften polluted).

Production of useful biomassFigure 8 shows the production of fresh biomass of theweed vegetation in the 6 × 1 m2 subplots, divided intoedge and interior plots, and for both cuts. The averageyield for the first cut was 464 g m-1 for the interior of thefield and 459 for the edge and the corresponding yieldsfor the second cut were 1042 g m-1 and 1006 g m-1 respec-tively. There were no statistically significant differences fordifferences in plot position (Tukey, p < 0.05), so wepooled the data of all plots for calculating production perhectare.

Useful spontaneous plants contributed 14.8 t ha-1 (freshweight) on the average, during the whole growing season.Of these, 9.7 t ha-1 were forage species (Simsia amplexicau-lis (Cav.)Pers.: 6.6 t ha-1, Bidens odorata Cav. 2.6 t ha-1) andthe rest were mostly food species (that can also be used asforage). Amaranthus hybridus L. produced 3 t and Chenopo-dium berlandieri Moq. 0.7 t per hectare, followed byBrassica rapa L. (0.6 t ha-1), Malva parviflora and Caland-rinia micrantha Schltdl. (both 0.4 t ha-1). Edible plants areusually harvested young, so they will not grow as abun-dantly as the forage plants that are harvested later. We alsoobserved a curious regularity: there were usually 1-3 edi-ble species in each m2 (Nanacamilpa: 2.1 ± 1.0; MiguelLira y Ortega: 2.5 ± 0.7; San Felipe 2.0 ± 0.9). Two medic-

inal/condiment plants, Rumex crispus and Polygonum avic-ulare L., produced less than 0.1 t ha-1.

Maize production was low: 1.5 t ha-1 in grain and 3.7 t ha-

1 (dry weight) in stover (straw, husk and rachis).

Economic costs and potential benefits of the useful biomassTable 2 shows the main components of the useful bio-mass production, maize grain, maize stover, wild vegeta-bles and forage, with their average production, sellingprice, cost of harvest and net return. From the total, thecultivation cost of 2500 pesos per ha has to be deducted.The average potential net value in 2006 was about 12,000pesos, that is over 1,000 US $ per ha.

DiscussionKinds of useful plantsThe number of plant species found in the maize fields, aswell as the number of useful plants and their uses coin-cides with other studies [12,22]. Also, it is common incentral Mexico that only a small proportion of agrestalweeds are not used in some way [22].

Commerce with wild plantsThe interviews show that highly informal channels suchas house-to-house sales may be of considerable impor-tance for rural families. This phenomenon was alsoreported by Vieyra and Vibrans [22], who found thatabout one third of the harvested quelites were sold withinthe community. The data also show that rural consumershave preferences as to the quality of the merchandise.

Production of useful biomassThe production of maize is relatively low, due to the shortgrowing season, and is similar to that reported previously

Table 1: Weeds of maize fields commercialized in the permanent and weekly markets of Nanacamilpa de Mariano Arista, Tlaxcala, Mexico (prices in Mexican pesos of 2006 and for fresh weight; 1 US Dollar = 10.50-11.00 pesos in that year).

Species (scientific and common name) Price Dry season(Oct-March)

Price Rainy season(May-Sept)

Amaranthus hybridus (quintonil) 15.00/kg 6.00/kg

Chenopodium berlandieri (quelite cenizo) 8.00/kg 5.00/kg

Calandrinia micrantha (lengüitas, chivitos) 8.00/kg 5.00/kg

Malva parviflora (malva) 8.00/kg 6.00/kg

Brassica rapa (nabo) 12.00/kg 5.00/kg

Gnaphalium sp. (gordolobo) 32.00-40.00/kg --------

Tagetes lucida (pericón) --------- 24.00-32.00/kg



from similar regions. The production of weed biomass isalso similar to that reported from other studies; otherstudies generally report dry weight. The majority of theforage weeds have a dry mass content of about 15-20%[29], so the 14.7 t fresh weight of useful weeds (forage +edible) would have a dry mass of approximately 3 t,almost as much as the maize component. This is similarto the data reported by Díaz [26] with 2.5 t ha-1 in the Val-

ley of Mexico. An experimental trial of cultivation of Sim-sia amplexicaulis as a forage crop in the state ofAguascalientes yielded 3.5 t ha-1 dry mass [30]. Mariaca[27] obtained 1.7 t ha-1 in a different type of ecosystem -the dry tropics of Yucatán - and in an experimental field.

We expected edge plots to have a higher weed productionthan the interior plots because of higher insolation, butdid not find this. The edge effects may be limited to thefirst meter approximately, and were not detected with ourmethods.

Economic costs and potential benefits of the useful biomassThe data show the regional economic importance ofmaize stover. The stover may command the same price asmaize grain (we priced it somewhat lower for our calcula-tions), probably because its price is regulated on a local orregional scale, whereas maize grain competes on theworld market. The often-overlooked economic impor-tance of straw production has been noted in other con-texts as well, for example in the traditional production ofwheat in Afghanistan [11].

Comparison of the average fresh biomass produced by weeds in the edge and interior plots (SD = standard devia-tion)Figure 8Comparison of the average fresh biomass produced by weeds in the edge and interior plots (SD = stand-ard deviation).

0

200

400

600

800

1000

1200

1st cut (April 2006) 2nd cut (July 2006)

Bio

mas

s (g

m-1

)

Field interior

Field edge

� � � � � �

� � � � � �

� � � � �

� � � � �

Table 2: Economic value of the average biomass production of maize fields in Nanacamilpa in 2006; in Mexican pesos (approximately 10.50 to 11.00 to an American dollar in that year).

Product Average production

Farm-level selling price

Cost of harvest/commercializa-

tion kg-1

Gross value Total cost of harvest/

commercialization

Net value

Forage (fresh weight)

9.7 ha-1 1.00 kg-1

(a)0.40 kg-1 9,700 ha-1 3,880 ha-1 5,820

Edible plants (quelites; fresh weight)

5 t ha-1 5.00 kg-1 4.00 kg-1

(b)25,000 ha-1 20,000 ha-1 5,000

Maize stover (dry weight)

3.7 t ha-1 1.00 kg-1 8.50/25 kg (packing machine)

3,700 ha-1 1,300 ha-1 2,400

Maize grain (dry weight)

1.5 t ha-1 1.30 kg-1 20.00 (harvest and degraining of

50 kg)

1,950 ha-1 600 ha-1 1,350

14,570.00- 2,500 cost of cultivation

Net economic value of

production

12,070.00 (ca. 1150 US $)

a) Amount based on relation with alfalfa (1.30 pesos kg-1 at farm level) and willingness-to-pay data.b) Whereas the majority of the products are or could be used within the farm, and can be calculated as being worth the farm-gate price of replacement or of a similar product, 5 t of edible herbs clearly exceeds the capacity of consumption of one family. We calculated 3 pesos/kg harvest cost (4 kg harvest/hour, cost of 1 h 12.50 pesos) and 1 peso/kg marketing cost (for transport to wholesaler, or sale within the community). - Edible plants can be used alternatively as forage, where they would have somewhat lower net worth (value is much lower, but costs are also less, because they don't have to be harvested separately by species).



The calculations show that the potential benefits from theweed vegetation are higher than those of the main crop.We concur with Maletta [11], who found an active marketboth for straw and for weeds as fodder, in the economicanalysis of wheat cultivation in Afghanistan,:"All thesefacts underline the necessity of including straw and weedsin the output of the wheat crop. Otherwise the cost ofgrain would be greatly overstated, and the benefit accru-ing to farmers greatly undervalued".

The economic valuation shows that these fields have avery high potential net return - about 1000 US $, compa-rable to some horticultural crops (and much higher thanthe 100 - 200 US $ ha-1 net return in intensive maize agri-culture), but with low external input and high stability ofthe system. High and Shackleton [14] presented data inthe same order of magnitude with an average return of667 US $ ha-1for an African system of home gardens.

Of course, this production is not completely used, becauseof the seasonal and general constraints on animal hus-bandry. But it serves as an economical stabilizer, as it canstill be used if the main crop fails, for example because ofa late frost.

A previous study of a similar region with a much highermaize productivity (because of access to early-season irri-gation and therefore a longer growing season) docu-mented that most farmers use some herbicides in order tokeep the weed vegetation low to facilitate harvest [22].However, they left parts unsprayed specifically for theweed harvest. We suggest that this non-crop production iseven more important both for direct use and for securityin the study region of this work, which is solely dependenton precipitation. Intensification that requires a reductionof the weed population would not easily be profitable,unless there are serious labor constraints. The role of non-crop plant resources in reducing risk of the rural popula-tion is often overlooked [14,31].

ConclusionThis study shows that maize grain - supposedly the mainpurpose of the cultivation - is actually a minor contributorto total productivity and potential net return in the exam-ined agricultural system, and worth less than the cultiva-tion costs. However, maize straw is worth considerablymore, and both together give a modest profit. Wild edibleherbs and especially forage make a major contribution,though it is only partially realized.

The spontaneous (weed) vegetation of a traditional agroe-cosystem can, under certain circumstances, be an econom-ically highly important part of the production, as well as arisk mitigator. It provides a simple explanation why farm-ers in the highlands of Mexico prefer these less-intensive

cropping systems, and why farmers in the tropics aremuch more likely do adopt intensive systems, as animalhusbandry and agriculture are less integrated in theseregions.

Moreover, there is room for improvement. As the usefulbiomass production is concentrated in a few months, it isonly partially used because of constraints during the restof the year. These constraints could be alleviated by con-serving the fodder biomass (through dehydration or fer-mentation), and investigation on these and other low-costalternatives to improve small-scale meat production.

This work shows that farmer's decisions are economicallyrational. It emphasizes the need to consider whole sys-tems when evaluating the economic viability of tradi-tional farming methods and for understanding farmer'sdecisions.

Competing interestsThe authors declare that they have no competing interests.

Authors' contributionsAll authors participated in the planning and design of thework; RGMA carried out the field work; RGMA and HVdrafted the first Spanish-language version of the manu-script, which was revised by AMB and FBP; HV wrote thefinal English-language version. All authors read andapproved the final manuscript.

AcknowledgementsWe thank the farmers and informants of Nanacamilpa for their time and patience; also the Consejo Nacional de Ciencia y Tecnología of Mexico for a grant to the first author, and Dr. Idah Madamombe-Manduna for her observations on the English and the manuscript.

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